Should I size up or down if I am between sizes?

Size up for any woven fabric, any closure that has to meet, anything lined or thick, and anything with a set sleeve. Size down for ruched or gathered designs, stretch knits that need tension, bias cuts and anything already cut deliberately loose.

Is it better for a dress to be too big or too small?

Too big, in almost every case, because a side seam can be taken in cheaply and a seam allowance of about 1cm means a garment cannot be let out. The exceptions are the shoulder on a structured piece and any design, like ruching, whose shape depends on being held taut.

Does sizing up make a dress longer?

Yes. Grading adds length, sleeve, shoulder width and neck opening along with the circumference, usually 1cm to 2cm of body length per size. On a short dress that can change the look, and on a wide neckline it can make the garment slide off the shoulder.

Should I size up in velvet?

Usually, if the piece is fitted and woven. The pile occupies real space, so velvet at a given flat measurement sits closer than a flat woven at the same number, and lining adds to that. A ruched or stretch velvet is the exception and wants the closer size.

Fit and sizing

Between two sizes: when to size up, when to size down, and how to break a tie

3 November 2026 · 5 min read

The standard advice is to size up when in doubt, and it is right often enough to be dangerous. Sizing up ruins a ruched dress, adds length you may not want, and puts a shoulder seam in the wrong place on anything structured. Sizing down is correct more often than people think, and wrong in a way that cannot be rescued when it is wrong. The decision is not about your body. It is about the fabric, the construction and which direction of error you can still wear.

Decide which measurement is between, first

Being between sizes at the bust on a fitted bodice is a different problem from being between sizes at the hip on a full skirt. Work out which of your measurements governs the garment, then only consider that one. A hip that falls between two sizes on a heavily pleated skirt is not a decision at all, because the hem has room to spare.

If the governing measurement is within about 2cm of both sizes, the chart has stopped being useful, since manufacturing tolerance is 1cm to 3cm anyway. At that point everything below applies.

If the governing measurement is clearly nearer one size, take that size and ignore the rest of this article. People talk themselves out of the obvious answer surprisingly often.

Size up for these

Any woven fabric with no stretch, and any closure that has to meet: a back zip, a row of buttons, a fitted band. A woven that is 2cm short at the closure does not close, and there is no wearing it in.

Anything with a set sleeve and a real armhole. The armhole is graded with the size, and a tight armhole restricts your arm long before the chest feels tight. It is also the most uncomfortable part of a garment to get wrong and the most expensive to alter.

Anything lined, interfaced or in a thick fabric. Velvet, a lining and a facing all take up room that the flat measurement does not show. A collared velvet dress with a fitted bodice is a size up candidate for all three reasons at once.

And anything where you intend to wear a layer underneath, which people forget until November.

Size down for these

Anything gathered or ruched, where the design is the tension. Ruching needs the fabric pulled to hold its gathers, and a size too big goes slack and reads as a crumpled dress rather than a shaped one. A dress gathered down the front is the clearest example on our own list: on this one, up is the wrong direction.

Anything with substantial elastane, where the fabric is meant to be held. A stretch knit at or slightly under your measurement sits smooth. The same knit a size up bags at the waist and rides.

Anything cut on the bias or in a heavy drapey fabric, because the weight stretches the garment downward and outward with wear. A bias cut piece grows on the body over an evening.

And anything already cut deliberately loose. If the flat chest measurement of a size S is 20cm larger than your bust, the next size up is not a slightly roomier version of the same garment. It is a different silhouette.

The tiebreak question

Ask which error you could still wear. Too tight is unwearable: it does not do up, it restricts, it pulls at the closure and it shows every seam. Too loose is usually wearable, and often fixable for the price of a short alteration.

That asymmetry is why size up is the default. Taking in a side seam is quick and cheap. Letting one out is normally impossible, because mass produced clothing is sewn with about 1cm of seam allowance and there is nothing there to release.

The two exceptions are the shoulder and the design itself. A shoulder seam that lands on your upper arm is a wrong garment, not a loose one, and no alteration shop will fix it for a sensible price. A ruched or stretch design a size too big has lost the thing it was for, and that is not a looseness you can take in either.

What sizing up also changes

A size up is not only wider. Garment grading adds length, sleeve, shoulder and neck opening at the same time, usually 1cm to 2cm of body length per size. That matters most on short garments and on short people.

A mini dress sized up is a slightly longer mini dress, which may be a relief or may remove the point of it. A piece that is short everywhere except the sleeves is working on exactly that proportion, so the extra length is part of the trade.

The neck opening grows too. On a square or wide neckline, a size up can slide off the shoulder, and on anything strapless or off the shoulder, going up is frequently the wrong move no matter what the chest measurement says.

A size up on trousers and skirts lengthens the rise, which is why a sized up waistband can sit higher than you intended and gap at the back.

Working through it on our own pages, and why it matters here

We do not take returns for a size chosen wrongly. That is a genuine disadvantage to you and it means a between sizes decision here costs more than it would at a shop with a returns desk. We would rather set that out than be reassuring about it.

So use the free tool. Email us with the item and your governing measurement before you order, and we will read the supplier's own flat measurements for that exact piece rather than quoting a general rule. Our overseas pieces do not run to a United States block, and we have written separately about how far apart the blocks sit.

If you are genuinely torn and the item is a fitted one, consider buying a forgiving thing from us first and learning how the sizing behaves on a lower risk purchase. A skirt with a deep pleat cares about one measurement and forgives the other two, which makes it a cheaper way to find out than a dress with a back zip.

Questions people actually ask

Should I size up or down if I am between sizes?: Size up for any woven fabric, any closure that has to meet, anything lined or thick, and anything with a set sleeve. Size down for ruched or gathered designs, stretch knits that need tension, bias cuts and anything already cut deliberately loose.
Is it better for a dress to be too big or too small?: Too big, in almost every case, because a side seam can be taken in cheaply and a seam allowance of about 1cm means a garment cannot be let out. The exceptions are the shoulder on a structured piece and any design, like ruching, whose shape depends on being held taut.
Does sizing up make a dress longer?: Yes. Grading adds length, sleeve, shoulder width and neck opening along with the circumference, usually 1cm to 2cm of body length per size. On a short dress that can change the look, and on a wide neckline it can make the garment slide off the shoulder.
Should I size up in velvet?: Usually, if the piece is fitted and woven. The pile occupies real space, so velvet at a given flat measurement sits closer than a flat woven at the same number, and lining adds to that. A ruched or stretch velvet is the exception and wants the closer size.